From: Lukasz Bartosik lb@semihalf.com
[ Upstream commit 7045465500e465b09f09d6e5bdc260a9f1aab97b ]
Fix invalid usage of a list_for_each_entry cursor in clk_notifier_unregister(). When list is empty or if the list is completely traversed (without breaking from the loop on one of the entries) then the list cursor does not point to a valid entry and therefore should not be used. The patch fixes a logical bug that hasn't been seen in pratice however it is analogus to the bug fixed in clk_notifier_register().
The issue was dicovered when running 5.12-rc1 kernel on x86_64 with KASAN enabled: BUG: KASAN: global-out-of-bounds in clk_notifier_register+0xab/0x230 Read of size 8 at addr ffffffffa0d10588 by task swapper/0/1
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.12.0-rc1 #1 Hardware name: Google Caroline/Caroline, BIOS Google_Caroline.7820.430.0 07/20/2018 Call Trace: dump_stack+0xee/0x15c print_address_description+0x1e/0x2dc kasan_report+0x188/0x1ce ? clk_notifier_register+0xab/0x230 ? clk_prepare_lock+0x15/0x7b ? clk_notifier_register+0xab/0x230 clk_notifier_register+0xab/0x230 dw8250_probe+0xc01/0x10d4 ... Memory state around the buggy address: ffffffffa0d10480: 00 00 00 00 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00 ffffffffa0d10500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9
ffffffffa0d10580: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
^ ffffffffa0d10600: 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00 ffffffffa0d10680: 00 00 00 00 00 00 00 00 f9 f9 f9 f9 00 00 00 00 ==================================================================
Fixes: b2476490ef11 ("clk: introduce the common clock framework") Reported-by: Lukasz Majczak lma@semihalf.com Signed-off-by: Lukasz Bartosik lb@semihalf.com Link: https://lore.kernel.org/r/20210401225149.18826-2-lb@semihalf.com Signed-off-by: Stephen Boyd sboyd@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/clk/clk.c | 30 +++++++++++++----------------- 1 file changed, 13 insertions(+), 17 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index af4f2ffc4fc5..9d60b3f219f6 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -2990,32 +2990,28 @@ EXPORT_SYMBOL_GPL(clk_notifier_register); */ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb) { - struct clk_notifier *cn = NULL; - int ret = -EINVAL; + struct clk_notifier *cn; + int ret = -ENOENT;
if (!clk || !nb) return -EINVAL;
clk_prepare_lock();
- list_for_each_entry(cn, &clk_notifier_list, node) - if (cn->clk == clk) - break; - - if (cn->clk == clk) { - ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb); + list_for_each_entry(cn, &clk_notifier_list, node) { + if (cn->clk == clk) { + ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);
- clk->core->notifier_count--; + clk->core->notifier_count--;
- /* XXX the notifier code should handle this better */ - if (!cn->notifier_head.head) { - srcu_cleanup_notifier_head(&cn->notifier_head); - list_del(&cn->node); - kfree(cn); + /* XXX the notifier code should handle this better */ + if (!cn->notifier_head.head) { + srcu_cleanup_notifier_head(&cn->notifier_head); + list_del(&cn->node); + kfree(cn); + } + break; } - - } else { - ret = -ENOENT; }
clk_prepare_unlock();